Plural potentiometer

ABSTRACT

A plural potentiometer in which independently and infinitely variable potentiometers are included in a common housing where for each potentiometer a resistive strip is applied to the inside of the housing and a leadscrew wiper nut, wiper, terminals and bearings are associated with each resistive strip to define the separate potentiometers. The leadscrews are suspended by bearings in end plates of the housing and independent means to turn each leadscrew is included.

United States Patent 1191 1111 3,846,733 Beetle Nov. 5, 1974 PLURAL POTENTIOMETER 3,585,560 6/1971 Schlesier 338/131 [75] Inventor: Ar hu B. Beetle Stpetersburg, 3,784,746 l/l974 Hess 338/128 Primary Examiner-Bruce A. Reynolds gn e TRW Elk Grove g 1 Attorney, Agent, or Firm-Lawrence S. Cohen [22] Filed: Oct. 19, 1973 Appl. No.: 408,097

U.S. Cl. 338/133, 338/180 Int. Cl H016 9/02 Field of Search 338/118, 128, 130, 131,

References Cited UNITED STATES PATENTS 5/1956 Leyerberger 338/180 X 11/1969 Hooter 338/128 [5 7] ABSTRACT A plural potentiometer in which independently and infinitely variable otentiometers are included in a common housing where for each potentiometer a resistive strip is applied to the inside of the housing and a leadscrew wipe nut, wiper, te rrr1inal s and bearings are associated with each resistive strip to define the separate potentiometers. The leadscrews are suspended by bearings in end plates of the housing and independent means to turn each leadscrew is included.

8 Claims, 9 Drawing Figures FIG;

llll FIG.

1 PLURAL POTENTIOMETER BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates generally to plural potentiometers and more particularly to a plural potentiometer where each potentiometer is independent and is infinitely variable.

2. Description of the Prior Art Plural potentiometers of the prior art consist generally of a single varying means and one or more resistive elements associated therewith. Such potentiometers usually require that all the resistors be varied if any one is to vary. While different resistance values can be given to the various resistive elements, so that each can give a different value atany one setting; nevertheless they are interdependent.

In another aspect of the prior art, potentiometers have been ganged by gears to a single adjuster. By putting a clutch or some other disengaging means between the shaft and the gears individual potentiometers may be subtracted from the gang. Such systems while useful for some purposes have the disadvantage of requiring relatively complex mechanism and concomitantly complex operability in a package large by standards of modern electronic packaging.

SUMMARY OF THE INVENTION The present invention provides a plurality of potentiometers each of which may be varied by its own independent adjustment. They are all packaged and may be sealed in a single'housing. External terminals permit convenient wiring to a circuit. Resistive strips are applied to the inside of the housing with a leadscrew, wiper nut, wiper terminals and bearings associated with each resistive strip so that by turning the leadscrew the wiper traverses the resistive strip effecting a variation in resistance in the circuit in which the potentiometer may be included. The leadscrew and its bearings are mounted in end plates of the housing with means to rotate the leadscrew at one end thereof.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view of half of the housing of a preferred embodiment.

FIG. 2 is an end view of the assembled housing of a preferred embodiment.

FIG. 3 is an end view of the adjustment end of a preferred embodiment.

FIG. 4 is a'partial sectional view through 4-4 of FIG.

FIG. 5 is a view of an embodiment of the terminal means taken as a partial sectional view through 5-5 of FIG. 4. I

FIG. 6 is a partial sectional view of the housing at one stage of the process.

FIG. 7 is a partial sectional view of the housing at another stage of the process.

FIG. 8 is a view of the shaft assembly.

FIG. 9 is a view of the wiper nut.

DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in FIGS. 1 and 2, a cylindrical housing 1 is made up of separate split halves la and lb. The split halves may bemade with a positive mating joint such as the rabbit joint 2. This joint assures accurate, fast assembly. For most purposes a high temperature sealing material such as an epoxy should be used to join the split halves. The housing is preferably made of a nonconductive material or the materials generally known as dielectric materials. A ceramic material is preferred.

A plurality of resistance strips 3 are formed on the inside surface 4 of the housing I. A method of forming the'resistance strips will be discussed below. For this explanation, eight potentiometers are described. Thus. eight resistance strips are formed on the surface 4, four on each half of 1a and lb of the housing I. The strips run axially along the inside surface, being generally parallel to each other and to the longitudinal axis of the cylindrical housing.

Referring to FIGS. 3 and 4, the housing is closed and sealed at its ends by a first end plate 5 and a second end plate 6. In this case again rabbit type joints 7 and 8 are suggested for ease of assembly and, with a good sealing material, dependable seal.

In this preferred embodiment, the first end plate 5 may be of an electrically conductive material such as steel while the second end plate should be a nonconductive, such as ceramic or other dielectric. Mounting holes such as at 9 may be conveniently provided although it is contemplated that for particular applications one or both of the end plates may be variously shaped for mounting purposes.

The eight lead screws 10 are located inside the housing between the end plates 5 and 6 and each one spaced from its associated resistance strip radially inward with respect to the axis of the housing. Thus, as shown in FIG. 3 the lead screws 10 are arranged in a circle concentric with the housing.

Each of the eight leadscrews 10 are fitted identically so that the following description applies to all of them. Referring to FIGS. 4 and 8 the leadscrew 10 is secured at one end in the first plate 5 by a shaft end 11 rotably mounted in a hole 12 in the plate 5. The shaft end 11 is made of an insulating'material such as nylon. The shaft end 11 is secured against axial motion by a shaft retaining pin 13 seated in hole 14 of the plate 5 and extending into a groove 15 in the shaft end 11. The shaft end 11 and the leadscrew 10 are connected by a reduced diameter portion 16 of the leadscrew l0 tightly fitted in a hole 17 in the shaft end 11.

The exposed end 18 of the shaft end 11 has some provision for its being rotated. In this case a screwdriver slot 19 is shown. The shaft end 11 may protrude from the end plate 5 as shown in the figures, or it may be flush or recessed, so long as some means is provided for rotating.

The shaft retaining pin 13 is secured against backing out of the hole 14 by placing a drop of epoxy or paint in the hole after the pin is in place.

It is apparent from this description that the leadscrew 10 is electrically isolated from the end plate 5 by the insulated shaft end 11, but that other means could be used to accomplish this.

The leadscrew 10 is mounted at the second end plate 6 in a combination wiper terminal and shaft bearing 20. This terminal is mounted in the end plate 6; its external portions being of a commonly known variety and like the terminals 28 to be described below.

Inside the end plate 6 the wiper terminal 20 has a lip 21 which holds a shaft end wiping contact 22 against .the end plate 6.The wiping contact 22 also bears on the shaft end contact 29 of the leadscrew 10. The shaft end contact 29 is preferably of semi-precious metal. The leadscrew terminates in a reduced diameter portion 23 which extends into the hole 24 of the combination wiper terminal and shaft bearing 20.

On the threaded portion 25 of the leadscrew 10 there is a wiper nut 26 also shown in FIG. 9, having a wiper 27 preferably of semi-precious metal which bears on the resistance strip 3.

As shown in FIG. 5, a terminal 28 is fitted through the housing to contact one end of the resistance strip 3. A second terminal may be fitted at the other end of theresistance strip. The exposed or external portions of the terminals 28 may be chosen from the commonly known varieties. They extend through the housing, al-

though preferably not through the resistance strip 3 but rather beside it. A tab 30 is secured such as by welding or brazing to the end of the terminals 28 and to the resistance strip 3. Other means for terminating may be chosen.

In use the eight potentiometers of the preferred embodiment herein described are wired into electrical circuits as desired and known to those familiar with them by means of the terminals, and the electrical resistance value of each potentiometer is varied as desired by rotating the insulated shaft end and with it the leadscrew. The wiper nut and wiper do not rotate being held against rotation by bearing force against the housing 1 and the resistance strip 3 of the wiper. Other means, such as a mechanical stop may be employed to prevent rotation of the wiper. As the leadscrew 10 is rotated the wiper nut 26 and wiper 27 translate axially, thereby varying the amount of the resistance strip included in the circuit and consequently the resistance in the circuit.

The multiple potentiometers are adapted to a process manufacture which is also part of the invention as hereafter described in its preferred embodiments.

The ceramic tube or cylinder halves la and lb are coated on their inside surface with a vitreous enamel resistance material or glaze such as is well known to those familiar with the art. In particular, the tube halves may be coated with a dip glaze by coating the entire part and then wiping off all but the inside surface 4. Then the parts are processed through a firing operation to cure the glaze. Thereafter the glaze material is removed from the areas 31 as shown on FIGS. 1 and 2 leaving only the resistance strips 3. This removal step may be done by vapor honing, sandblasting or other means, as desired. Finally, the electrical resistance of each of the' strips is adjusted in a known manner to the desired range of resistance by removing some of the resistance material. It is similarly possible to adjust the resistance values of each of the resistance strips so that different total resistance values may be obtained in one package.

In another embodiment of the process as shown in FIGS. 6 and 7 the housing is formed with grooves thereby providing a spline-like structure as shown, including a root 32 and a crest 33. The entire inside surface is coated with a resistor glaze material 34 and fired as described above. Then the resistor glaze material is removed in a single step or pass from the crests 33 such as by diamond honing or other reaming process leaving only the resistor glaze material 35 left in the grooves, forming the resistance strips. These are-adjusted to the desired resistance as previously described.

By this invention a numberof independently and infinitely variable potentiometers may be included in a single package of such small size to be useful with the complex and compact electronic packages in current use. The number of potentiometers in a unit of the invention and indeed the preferred embodiment described herein may be modified without departing from the essential natureof this invention and all changes and modifications which do not constitute departures from the scope of the invention are intended to be covered by the appended claims. w

I claim:

1. A multiple independently and infinitely variable potentiometer instrument comprising:

an elongated housing having a closed curve cross section of dielectric material;

a plurality of resistance elements axially disposed on the inner surface of the housing;

' first and second end plates secured to and closing the ends of the housing;

a plurality of electrically conductive leadscrews each associated with one resistance element by having its ends rotatably mounted in the end plates and each leadscrew being spaced from its associated resistance element radially inward with respect to the axis of the housing, and parallel thereto;

adjustment means at one end of each leadscrew enabling independent rotation thereof;

means for electrically isolating the leadscrews from each other; 7

a wiper nut on each leadscrew and having a wiper portion thereof in contact with its associated resistance element;

a plurality of first terminal means each associated with at least one resistance element at one end thereof;

a plurality of second terminal means each associated with at least one leadscrew.

2. The instrument of claim 1 wherein each of the ad- 40 justment means is an insulating shaft end extending through the first end plate and supporting its respective leadscrew thus, electrically isolating each leadscrew at the first end plate.

3. The instrument of claim l wherein the second terminal means are mounted on the second end plate and also provide a shaft bearing for mounting therein its associated leadscrew.

4. The instrument of claim 3 wherein the second terminal means also have a wiping contact bearing against the leadscrew.

5. The instrument of claim 1 further comprising a plurality of third terminal means each associated with one resistance element in electrical contact with the end of its associated resistance strip opposite that of the first terminal means.

6. The instrument of claim 5 wherein each first terminal extends through the housing adjacent its associated resistance strip and has a tab extending from its interior end to the resistance strip.

7. The instrument of claim 1 wherein each first terminal extends through the housing adjacent its associated resistance strip and has a tab extending from its interior end to the resistance strip.

8. The instrument of claim 1 wherein the resistance elements are a cured vitreous enamel resistance mixture fused to the inner surface of the housing.

li l 

1. A multiple independently and infinitely variable potentiometer instrument comprising: an elongated housing having a closed curve cross section of dielectric material; a plurality of resistance elements axially disposed on the inner surface of the housing; first and second end plates secured to and closing the ends of the housing; a plurality of electrically conductive leadscrews each associated with one resistance element by having its ends rotatably mounted in the end plates and each leadscrew being spaced from its associated resistance element radially inward with respect to the axis of the housing, and parallel thEreto; adjustment means at one end of each leadscrew enabling independent rotation thereof; means for electrically isolating the leadscrews from each other; a wiper nut on each leadscrew and having a wiper portion thereof in contact with its associated resistance element; a plurality of first terminal means each associated with at least one resistance element at one end thereof; a plurality of second terminal means each associated with at least one leadscrew.
 2. The instrument of claim 1 wherein each of the adjustment means is an insulating shaft end extending through the first end plate and supporting its respective leadscrew thus, electrically isolating each leadscrew at the first end plate.
 3. The instrument of claim 1 wherein the second terminal means are mounted on the second end plate and also provide a shaft bearing for mounting therein its associated leadscrew.
 4. The instrument of claim 3 wherein the second terminal means also have a wiping contact bearing against the leadscrew.
 5. The instrument of claim 1 further comprising a plurality of third terminal means each associated with one resistance element in electrical contact with the end of its associated resistance strip opposite that of the first terminal means.
 6. The instrument of claim 5 wherein each first terminal extends through the housing adjacent its associated resistance strip and has a tab extending from its interior end to the resistance strip.
 7. The instrument of claim 1 wherein each first terminal extends through the housing adjacent its associated resistance strip and has a tab extending from its interior end to the resistance strip.
 8. The instrument of claim 1 wherein the resistance elements are a cured vitreous enamel resistance mixture fused to the inner surface of the housing. 